For vibrationless efficient operation of equipment that utilizes crankshafts with multiple throws, the throws must be machined precisely parallel and accurately displaced angularly from one another. In the past, "two-throw" crankshafts have been chucked with one of the throws on centerline of lathe rotation for machining the first throw. The crankshaft has then been removed and rechucked in a second chuck with the second throw on centerline of lathe rotation for machining the second throw. The rechucking introduces alignment and orientation errors between the first and second throws.
One object of this invention is to provide a first and second precise positioning of the two throws without rechucking, thus eliminating the errors introduced by multiple chucking of the crankshaft.
Another object is to eliminate the labor and production time lost in the second handling of the crankshaft which involves the unclamping, unloading, reloading in a second chuck, and reclamping the part with the second throw on centerline of lathe rotation.
Another object is to provide a part chuck which consists of a relatively few simple parts, is rugged and durable in use, is capable of being inexpensively manufactured, and will operate reliably in a contaminated cutting tool environment.
These and other objects, features and advantages of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.